Method of prepregging with resin and novel prepregs produced by such method

ABSTRACT

Disclosed is a process of forming a prepreg material having substantially no voids. According to the process of the invention, the reinforcing material is heated to a temperature above the temperature of the impregnating resin. The prepreg formed has substantially no voids and does not require lengthy consolidation when formed into useful articles.

FIELD OF THE INVENTION

[0001] The present invention relates to apparatus and method ofprepregging materials such as fibers or other such reinforcements withresinous materials, especially with thermoplastic resin compositions.The invention further relates to prepregs produced by such apparatus ormethods and to a method of using such prepregs to form articles havinghighly desirable properties.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] Reinforced thermoplastic and thermoset materials have wideapplication in, for example, the aerospace, automotive,industrial/chemical, and sporting goods industries. Thermosetting resinsare impregnated into the reinforcing material before curing, while theresinous materials are low in viscosity. Thermoplastic compositions aremore difficult to impregnate into the reinforcing material because ofcomparatively higher viscosities. On the other hand, thermoplasticcompositions offer a number of benefits over thermosetting compositions.For example, thermoplastic prepregs are easier to fabricate intoarticles. Another advantage is that thermoplastic articles formed fromsuch prepregs may be recycled. In addition, a wide variety of propertiesmay be achieved by proper selection of the thermoplastic matrix.

[0003] Fiber-reinforced plastic materials are usually manufactured byfirst impregnating the fiber reinforcement with resin to form a prepreg,then consolidating two or more prepregs into a laminate, optionally withadditional forming steps. Consolidation is typically necessary to removevoids that result from the inability of the resin to fully displace airfrom the fiber bundle, tow, or roving during the processes that havebeen used to impregnate the fibers with resin. The individuallyimpregnated roving yarns, tows, plies, or layers of prepregs are usuallyconsolidated by heat and pressure, or with heat and vacuum as byvacuum-bag molding and compacting in an autoclave. The consolidationstep has generally required the application of very high pressures orvacuums at high temperatures and for relatively long times.

[0004] In the past, a thermoplastic composition has typically beenheated, slurried, commingled, or diluted with solvents in order toreduce the viscosity of the composition before it is used to impregnatethe reinforcing material. These methods have suffered from seriousdrawbacks. In the case of using solvent to reduce viscosity, the solventmust be driven off after the impregnation step, resulting in anadditional step in the process as well as unwanted emissions. Moreover,the desired matrix may be insoluble in common solvents. In the case ofheating the thermoplastic matrix in order to reduce its viscosity, thedwell time of the resin in the heated zone may result in degradation ofthe resin with attendant decrease in the desired mechanical properties.Furthermore, the molecular weight of the resin may need to be kept lowerthan would be desired for properties of the ultimate product in order tofacilitate the impregnation step. Finally, as noted above, knownprocesses for impregnating thermoplastic resin into reinforcingmaterials have required lengthy consolidation of the prepreg materialsat high temperatures and pressures in order to develop the best physicalstrength and other properties and to minimize or eliminate outgassingduring the consolidation or in later steps, e.g., finishing processes.Outgassing during consolidation results in voids within the compositethat can cause microcracking or premature delaminiation that mayadversely affect mechanical properties; outgassing during coating stepstends to cause pinholing or popping in the substrate or coating,resulting in an undesirably rough and blemished surfaces or finishes.

[0005] Cochran et al., U.S. Pat. No. 5,236,646, disclose that a processusing vacuum of up to about 28 inches of mercury below atmosphericpressure and temperatures above the melting point of the resin requiresa shorter time for consolidation as compared to a process that uses highconsolidation pressures of from about 100 to 300 psi. However, theconsolidation step still requires a dwell time under vacuum of up tosixty minutes or more.

[0006] Because the length of time typically required to properlyconsolidate the prepreg plies determines the production rate for thepart, it would be desirable to achieve the best consolidation in theshortest amount of time. Moreover, lower consolidation pressures ortemperatures and shorter times will result in a less expensiveproduction process, for instance due to lowered consumption of energyper piece for molding.

[0007] The present invention provides a new process for preparingprepregs, novel prepregs, and articles of reinforced materials thatoffers significant advantages over the processes described above. In themethods according the present invention, the reinforcing material isheated before being impregnated with the resinous matrix composition.The impregnated roving or tow that is produced according to the presentinventive process has substantially no voids and can therefore bequickly and easily formed into a desired article having no voids oressentially no voids without the lengthy consolidation processesnecessary for prepregs formed by other processes. In other words, theroving bundle is fully, or substantially fully, wet out. The onlyprocess that must take place in forming an article is fusion betweenimpregnated bundles, and it is possible to use temperatures, pressures,and/or times during such forming operations that are significantlyreduced over prior art processes.

[0008] The present invention also provides a method of making a moldedarticle using the prepreg of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic diagram for a preferred apparatus of theinvention used in a method of the invention that is demonstrated byExamples 1 and 2.

[0010]FIG. 2 is a schematic diagram for a preferred apparatus of theinvention used in a method of the invention that is demonstrated byExample 3.

[0011]FIG. 3 is a schematic diagram for a preferred apparatus of theinvention used in a method of the invention that is demonstrated byExample 4.

DETAILED DESCRIPTION

[0012] The process of the invention includes heating the fiber or otherreinforcing material; bringing the heated reinforcing material intocontact with the matrix resin composition under an applied shear to forma prepreg; and, optionally, further forming the prepreg into a desiredshape. The invention further provides a prepreg formed thereby havingexceptionally few voids or substantially no voids that can be formedinto a desired product more quickly and easily than prepregs that arenow known in the art. Presence of voids may be determined or measured bymeasuring the density of the prepreg or article or by visual observationwith the aid of a microscope.

[0013] The term “prepreg” as used herein preferably refers to acomposite, whether in rod, rope, fiber, roving, strand, tow, sheet, orother form, which comprises a reinforcing fiber or other such substrateimpregnated with a matrix composition. The present process is especiallyuseful when the resin is a thermoplastic resin. However, the method ofthe invention may also be utilized for uncured or partially curedthermoset resins. The present invention is particularly advantageous forthermosetting composition when the viscosity of the composition at thedesired processing temperature would otherwise make processing difficultor result in degradation of the resin. For example, the present methodsare particularly suitable for so-called “pseudo thermoplastic” materialsthat exhibit behaviors during prepregging similar to those of truethermoplastic materials. The present inventive processes are alsoadvantageous for heating the reinforcing material to a temperature thatwill cause partial curing of the thermosetting material when suchpartial curing is desired before forming the final article. Finally, theinvention includes a method of thermoset prepregging for thermosettingcompositions having a short “pot life” at the temperature needed toproduce a suitable resin viscosity. “Pot life” is a term of art thatdescribes the interval of time after mixing during which a thermosettingcomposition may be used before it sets up (i.e., before the viscositybuild up due to crosslinking makes the composition unworkable).

[0014] All types of fiber reinforcements or other reinforcing materialscommonly used for these applications may be used in the processes of theinvention. It is also possible for a roving bundle or tow to be shapedbefore being impregnated, for example to be flattened to a tape, or forthe reinforcing fiber to be used as a cloth. Useful fibers include,without limitation, glass fibers, carbon and graphite fibers, polymericfibers including aramide fibers, boron filaments, ceramic fibers, metalfibers, asbestos fibers, beryllium fibers, silica fibers, siliconcarbide fibers, and so on. The fibers may be conductive and suchconductive fibers, for example conductive carbon fibers or metal fibers,may be used to produce articles for conductive or static chargedissipative applications or EMI shielding.

[0015] Glass fibers, in particular, are available in a number ofdifferent kinds, including E-glass, ECR-glass (a modified E-glass thatis chemically resistant), R-glass, S-glass and S-2 glass, C-glass, andhollow glass fibers. For many applications glass fibers of highermodulus will be preferred; thus, the order of preference among the glassfibers from more preferred to less preferred is S-2, C, R, then E.Commercially available fibers include Nenxtel™ ceramic fiber (from 3M);Vectran™ (from Hoëchst-Celanese); and Hollow-X™ (from Owens-Corning).

[0016] The fiber filaments are usually formed into a bundle, called aroving or tow, of a given uniform cross-sectional dimension. The fibersof the bundle are usually all of the same type, although this is notessential to the present method. For a particular impregnating matrixcomposition, a reinforcement should be chosen that can withstanding thetemperatures and shear suitable for producing the desired prepreg. Inparticular, if a fiber is coated with a sizing or finishing material,the material should be one that is stable and remains on the fiber atthe selected processing temperature. A sizing or finishing material, ifemployed, may be selected and applied according to customary means.Unsized fibers such as carbon are advantageously employed in someapplications in order to optimize mechanical properties.

[0017] In one preferred embodiment, fiberglass filaments are impregnatedwith a thermoplastic resin. Fiberglass filaments typically are coatedwith a sizing and/or finishing material. The sizing material orfinishing material used is selected to be able to withstand thetemperatures to which the fiberglass is heated during the process. Onepreferred sizing is Owens Corning 193/933.

[0018] The fiber bundle, mat, cloth, or other reinforcing material isheated to a selected temperature above the melting point, softeningpoint, or glass transition temperature (T_(g)) of the impregnating resinmatrix composition. (Which of these—melting point, softening point, orT_(g)—a particular composition has depends upon the particularcharacteristics of the composition, as whether the composition comprisesan amorphous or crystalline impregnating resin, but is not critical tothe invention.) The temperature to which the fibrous reinforcingmaterial is heated is sufficient to produce a prepreg having no voids orsubstantially no voids. The temperature to which the fibrous reinforcingmaterial is heated is thus sufficient to cause the impregnating resin tofully or substantially fully wet out the fibrous reinforcing material.In a preferred embodiment of the invention, the reinforcement is heatedto at least about 25° F., preferably to at least about 50° F., stillmore preferably to at least about 75° F., and even more preferably to atleast about 100° F. above the melting point, softening point, or T_(g)of the resin matrix composition; and up to about 500° F., preferably upto about 400° F., particularly preferably up to about 350° F., and evenmore preferably up to about 300° F. above the melting point, softeningpoint, or T_(g) of the resin matrix composition. In a preferredembodiment, the reinforcing material is heated to a temperature aboveabout 350° F., and below about 800° F. Some considerations in thechoosing a particular temperature to which to heat the reinforcementwill be the distance that it must travel through the resin bath, thespeed with which it is pulled through the bath, the viscosity of theresin in the bath, and the shear produced at the surface of thereinforcement. Because the length of time to which the matrix resincomposition is exposed to such temperature is relatively short, theroving bundle or tow may be heated even to temperatures that mightotherwise cause thermal degradation of the matrix resin composition.

[0019] The means for heating the fiber is not generally critical, andmay be chosen from any number of means generally available for heatingmaterials. Particular examples of such means include, withoutlimitation, radiant heat, inductive heating, infrared tunnels, orheating in an oven or furnace, e.g. an electric or gas forced air oven.Insufficient heating may result in undesirable resin conglomeration atthe surface of the roving bundle, tow, or other reinforcement. Thus, thetemperature to which the roving bundle is heated should be sufficient toallow the resin to flow between the filaments or fibers to impregnatethe roving or tow in a substantially uniform way. The methods of theinvention allow the resin matrix composition to impregnate the fiberbundle instead of agglomerating at the surface of the fiber bundle. Theparticular temperature chosen will depend upon factors that would beobvious to the person of skill in the art, such as the particular typeof resin used, the denier of the fiber, and the profile or size of thebundle and can be optimized by straightforward testing according to theultimate application method. Preferably, the reinforcing material isheated above the temperature of the impregnating matrix composition. Ina preferred embodiment of the present process, fiberglass coated withOwens Corning 193/933 sizing is heated to above about 350° F., and belowabout 800° F.

[0020] The matrix resin compositions used in the methods of theinvention may be thermoset or, preferably, thermoplastic resincompositions. Virtually any thermoplastic resin suitable for forminginto articles by thermal processes, molding, extrusion, or other suchprocesses may be employed in the methods of the invention. For example,and without limitation, the following thermoplastic materials mayadvantageously be used: acrylonitrile-butadiene-styrene (ABS) resins;acetal resins; acrylics; acrylonitriles (AN); allyl resins; cellulosics;epoxies; polyarylether ketones; polyether etherketones (PEEK); liquidcrystal polymers, such as those sold under the tradename Xydar by AmocoPolymers Inc., Atlanta, Ga.; amino resins, including melamine, melamineformaldehyde resins, urea formaldehyde resins, guanidines, and so on;phenolics; polyamides, such as poly(tetra-methylene) adipamide andpolyphthalamide; polyimides; polyamide-imide resins; polyolefins, suchas polyethylene, polypropylene, and polybutylene homopolymers andcopolymers; polycarbonates; polyesters, such as polyalkyleneterephthalates including, without limitation, polybutylene terephthalate(PBT) and polyethylene terephthalate (PET); polyimides andpolyetherimides; polyphenylene oxide; polyarylene sulfites such aspolyphenylene sulfite; polyarylene sulfides such as polyphenylenesulfide; polyvinyl resins, including, without limitation,polystyrene(PS) and copolymers of styrene such as styrene-acrylonitrilecopolymer (SAN), polyvinyl chloride (PVC), and polyvinylphenylenechloride; polyurethanes; and polysulfones, including, withoutlimitation, polyaryl-ether sulfones, polyether sulfones, and polyphenylsulfones. The thermoplastic resins may have melting points, softeningpoints, or T_(g)s ranging up to about 750° F. Mixtures of two or moreresins may also be used. Preferred thermoset resin compositions includeepoxies that cure with amines, acids, or acid anhydrides and polyestersthat cure through unsaturation, as well as bismaleimides, polyimides,and phenolics.

[0021] The matrix compositions may include one or more additives, suchas impact modifiers, mold release agents, lubricants, thixotropes,antioxidants, UV absorbers, heat stabilizers, flame retardants,pigments, colorants, nonfibrous reinforcements and fillers,plasticizers, impact modifiers such as ionomers or maleated elastomers,and other such customary ingredients and additives. In the case of athermoset resin composition, a catalyst or initiator for the curingreaction may advantageously be included.

[0022] The apparatus of the invention includes a heater for heating thefibrous reinforcing material and a container in which the moltenimpregnating resin composition is disposed. The container has an inletthrough which the fibrous reinforcing material enters the container andan outlet through which the fibrous reinforcing material exits thecontainer. The heater is located so that it can provide the fibrousreinforcing material to the inlet to the container with the fibrousreinforcing material being at a temperature that is sufficient toproduce a prepreg having no voids or substantially no voids. Thetemperature to which the fibrous reinforcing material is heated is thussufficient to cause the impregnating resin to fully or substantiallyfully wet out the fibrous reinforcing material. In particular, theheater is one that is capable of heating the reinforcing material to atemperature above the temperature of the molten matrix resin, and,preferably, the heater is one that is capable of heating the reinforcingmaterial to a temperature of above about 350° F. and up to about 800°F., as measured at the inlet of the container. While in the container,the fibrous reinforcing material passes through a shearing mechanism.The container may be, for example, a tank, an extruder, an impregnationdie, or any other container of suitable size to accommodate both theresin and the fibrous reinforcing material and to provide the shearingmechanism. For example, the container may be a tank having as an inlet atapered die, as an outlet a sizing die, and as a shearing mechanism apair of shear pins. The container may further comprise an openingthrough which pressure is applied to the molten resin, for example by apiston. In another example, the container may be an impregnation die,having an inlet for a fiber, an inlet for resin, a pair of die shearpins through which the fiber is pulled, and an outlet. Optionally, theapparatus of the invention further includes molding equipment forforming the prepreg into an article of a desired shape.

[0023] In one aspect of the invention, the heated roving bundle is movedthrough a bath of molten impregnating matrix resin composition,preferably with a shear sufficient to aid in the flow of the resin intothe roving bundle. Shear may be created by moving a roving across twodisplaced and opposing pins located in the matrix resin bath. Shearforce may be created by applying tension to the fiber or roving bundlewhile the fiber or roving bundle is passing over and around these pins.Greater shear may be created by increasing the separation of the pins orby increasing the tension on the creel, for example with the aid of amagnetic brake. In general, the shear should be increased when theviscosity of the resin increases. In a preferred-embodiment, the fibersare heated to a temperature approaching the degradation temperature ofthe resin. At higher temperatures, the viscosity of the resin that comesinto contact with the heated fiber is minimized and, consequently, theshear required to move the fiber through the resin is minimized.

[0024] After the fibers of the roving or tow have cooled toapproximately the temperature of the matrix resin bath, the amount ofresin adhering to the exterior of the bundle may be increased ordecreased in order to achieve a desired ratio of resin to fiber for theimpregnated bundle. In particular, the impregnated roving bundle may befed through a shearing mechanism at a rate that will allow laminar flowof the resin, and then through a sizing die, in order to give the rovingor tow its final desired shape and resin percentage. The roving or towmay then be wound onto creels, chopped into strands of a desired length,for example at least about 3 mm in length, and up to about 76 mm inlength, or used immediately in a pultrusion or forming operation. A tapeor cloth may also, for example, be wound onto a creel for use in a laterforming process.

[0025] The apparatus of the invention, in another embodiment, includes aheater for heating the fibrous reinforcing material and a compressingunit for pressing the heated fibrous reinforcing material together witha solid body of a matrix resin composition. The heater is located sothat it can provide the fibrous reinforcing material to the compressingunit with the fibrous reinforcing material being at a temperature thatis sufficient to produce a prepreg having no voids or substantially novoids. The temperature to which the fibrous reinforcing material isheated is thus sufficient to cause the impregnating resin to fully orsubstantially fully wet out the fibrous reinforcing material. Inparticular, the heater is one that is capable of heating the reinforcingmaterial to a temperature above the melting point, softening point, orglass transition temperature of the matrix resin, and preferably atemperature above about 350° F. and up to about 800° F., as measured atthe point where the reinforcing material enters the compressing unit.

[0026] A mat or sheet may be preheated as described and then compressedwith the matrix resin composition into a sheet of laminate. Sheetmolding compounds may be produced according to this variation of thepresent process.

[0027] In general, the prepregs of the invention may comprise from atleast about 1% by weight resin, and up to about 150% by weight resin,based upon the weight of the fiber. The preferred ranges of the weightof resin included in the prepreg will depend upon the specific resin andreinforcing material used, as well as upon the desired properties anduse of the article to be formed by the process. Optimum ratios of resinto fiber may be determined according to known methods. In a preferredembodiment, the resin is at least about 25% by weight, and up to about75% by weight, based upon the weight of the reinforcing fiber.

[0028] The preferred impregnated roving or tow produced according to theinventive methods may be described as a “fully impregnated” roving ortow; that is, the interface between the fibers and the resin issubstantially free of voids. An impregnated fiberglass roving, forexample, has a set and uniform dimension with a given amount ofthermoplastic resin matrix. This impregnated roving can be moldedquickly into a finished part having substantially no voids and havingexcellent properties without the need for a lengthy or rigorousconsolidation step. Thermoplastic composite matrices are preferred overthermoset matrices when properties of toughness, capacity for recyclingand/or reforming and/or post-forming of the piece, resistance to UVdegradation, or other specific properties available in thermoplasticmediums are required.

[0029] It is known in the art that the properties developed in the finalarticle are dependent upon the impregnation process and theconsolidation and other fabrication steps following impregnation. Thisis particularly true for high viscosity thermoplastics that areimpregnated neat (that is, without including solvent). The prepregsproduced according to the methods of the invention have uniformdimensions, homogenous distributions of the impregnated resin, and arepreferably essentially free of voids.

[0030] The impregnated fibers of the invention may be used asunidirectional, woven (e.g., fabric), or random (chopped) materials. Thefibers may be used as unidirectional tows, such as those of 3000, 6000,and 12,000 filaments per tow that are usual in the industry, typicallyof lengths up to about 1000-m (3000-foot). The fibers may also be formedinto unidirectional tapes, such as tapes having the typical dimensionsof 150-mm (6-inch) or 300-mm (12-inch) widths and lengths of up to 50 m(150 feet). Tapes typically range from about 80 g/m² to about 190 g/m²,and a typically 0.125 mm (5 mils) thick. Prepreg unidirectional tow mayoptionally be woven into a fabric.

[0031] The prepreg of the invention is cut or trimmed to a desiredshape. Plies can be trimmed from a prepreg roll into the desired shape,size, and orientation by means of any cutting device known in the art.Plies can be stacked by hand or by machine in what is known in the artas a lay-up operation.

[0032] Continuous directional fibers may be formed by compressionmolding, filament winding, pultrusion, or combinations of theseprocesses. Compression molding is usually employed for forming complexshapes and is used in a preferred embodiment of the invention.

[0033] The assembled plies may be consolidated using heat or acombination of heat with either pressure or vacuum for a period of timesufficient to consolidate the plies. The time of consolidation ispreferably from about 1 minute to about 20 minutes at a temperaturepreferably greater than the melting point, softening point, or Tg of theresin matrix, preferably at least 20° C. above the melting point,softening point, or Tg of the resin, and particularly preferably aboveabout 20° C., and below about 100° C. above the melting point, softeningpoint, or Tg of the resin. Optionally, additional resin may be added tohelp bind or ply the tows together, particularly in a pultrusionprocess.

[0034] A typical pultrusion process involves thermal shaping and, in thecase of a thermoset composition, optional curing of the prepreg.Pultrusion is an automated process for manufacturing composite materialsinto linear, continuous profiles having constant cross-sections.Typically, the pultrusion process begins with reinforcing fibers thatare strung from creels at the beginning of the equipment to pullers atthe end. The fibers typically pass through a resin bath where they areimpregnated with resin. The resin impregnated fibers are continuouslypulled through a die that typically has both cooling and heating zonesto fashion the final shape of the profile. The heating zone maypartially cure a thermosetting resin. The pullers continuously pull theprofile toward a flying cutoff saw that cuts the pultruded compositeinto the desired lengths.

[0035] The prepreg may be formed into articles according to any of themethods known in the art. For example, a compression molding or vacuummolding process may be used. Other processes, such as injection molding,thermoforming, blow molding, calendering, casting, extrusion, filamentwinding, laminating, injection molding, rotational or slush molding,transfer molding, lay-up or contact molding, or stamping may be usedwith the impregnated materials formed by the present methods.

[0036] The methods of the invention may be used to form many differentkinds of useful articles. Examples of such articles include, withoutlimitation, air bag canisters, bumper beams, frame cross members, highstrength brackets, leaf springs, seat frames, skid plates, torsion bars,wiper arms, fencing, gears, highway reinforcing rod, pipe hangers, powerline cross arms, boat trailers, outboard engine cowlings, bow limbs, cartop carriers, and horse shoes. The inventive methods and novel prepregsmay be advantageously used to form any article that might be formedusing previously known prepregs and methods.

[0037] The invention is illustrated by the following examples. Theexamples are merely illustrative and do not in any way limit the scopeof the invention as described and claimed. All parts are parts by weightunless otherwise noted.

EXAMPLE 1

[0038] Referring now to FIG. 1, 1 kg of amorphous nylon resin (Grivory21, available from EMS-American Grilion Inc., Sumpter, S.C.) is chargedto resin tank 2 between heated platens 4 and 6. The resin is heated toabout 465° F. under a pressure of about 28 psi applied from piston 8. Aroving of S2 glass (750 yield, 933 sizing, available from Owens Corning,Corning N.Y.) is pulled from a creel 10 and through an 18 inch radiantheat tube 12, the tube being heated to a temperature of about 595° F.Exiting the heat tube, the roving is passed through a tapered fiberinlet die 14, over and around two 0.3 inch radius shear pins 16 and 18heated to 495° F. and positioned about one inch apart horizontally andabout 1.5 inches apart horizontally in the resin bath, and finallythrough a sizing die 20 located opposite the inlet die. The sizing diehas a rectangular cross section with a dimensions of 0.25 in.×0.009 in.The hot fiber is pulled at a rate of about 42 ft/min. through the bath.The resulting impregnated tow is 0.25 in. wide, 0.0095 in. thick, andhas no measurable air void content. The impregnated tow is wrapped ontoa flat 2-bar rotating creel 22. Forty-nine wraps, 2 in. wide, are madeon the creel. The wound creel is then place into a pre-heated tool at480° F. and 200 psi for 8 minutes. The tool is then quenched. Theresulting part is 18 inches long, 2 inches wide, and 0.175 inch thickwith no measurable void content.

EXAMPLE 2

[0039] A tow of S2 glass (750 yield, 933 sizing, available from OwensCorning, Corning N.Y.) is impregnated with amorphous nylon resin(Grivory 21, available from EMS-American Grilion Inc., Sumpter, S.C.)using the same procedure described in Example 1, except that theresulting impregnated tow is sized to 0.25 in. wide and 0.011 in. thick.The impregnated tow has a resin content of 54% by weight. Theimpregnated tow is chopped into three-inch section. The choppedimpregnated tow, 713.25 grams, is placed into a 10 in.×18 in. tool thatis preheated to 515° F. and is pressurized to 300 psi for 8 min. Thetool is then quenched. The resulting part weighs 653 grams and has anaverage thickness of 3.82 mm.

EXAMPLE 3

[0040] A woven S2 fiberglass cloth with Owens Corning 933 sizing isimpregnated with the same amorphous nylon resin and is used in Examples1 and 2. The fiberglass cloth has the following parameters: FDI Style #1406 (a designation of Fabric Development Corporation, Quakertown, Pa.);yarn type, S2 glass 75 1/0, 933A; weave, 8 harness satin; count, 120×30;width, 39.25 in.; weight, 11.74 oz per square yard; and thickness,0.0017 in. as measured at 1 psi.

[0041] The nylon is extruded into a film 0.0045 in. thick and placed ona creel. The S2 cloth is also on a creel.

[0042] Referring now to FIG. 2, the nylon film 24 is pulled from creel26 and the glass cloth 28 is pulled from creel 30. The glass cloth ispulled through a radiant heater 32. The radiant heater heats the fiberto 600° F., while a reinforced Teflon® sleeve 34 on top of the heatercarries the film. Heat escaping from the heater raises the temperatureof the film to between 425 and 475° F. The cloth and the film are thenfed into two pair of 36-inch compaction rollers 35 and 36. Thecompaction rollers are covered with Teflon® and two inches of siliconerubber. The rollers exert a force of from 700 to 800 psi on the film andcloth. The impregnated cloth is taken up on creel 38.

[0043] The impregnated cloth is cut into sections 10 in.×18 in. Eightplies are then stacked into a preheated (525° F.) tool and compressed at300 psi for 12 minutes. The tool is then quenched. The resultinglaminate is uniform and 0.128 in. thick.

[0044] Parts prepared according to the procedures in the above Examples2 and 3 were tested for physical properties with the following results.Example 2 Example 3 Tensile 32.81 134.8 Stress (ksi) Young's 2.001 6.253Modulus for Tensile Stress (Msi) Loss on 58.752 31.894 Ignition (LOI)Glass Content 41.246% 68.106 (wt %) Compressive 46.74 90.43 Stress (ksi)Young's 2.088 7.271 Modulus for Compressive Stress (Msi)

EXAMPLE 4

[0045] A polyethylene terephthalate, glycol addition resin (melttemperature=195.8° F., available from Eastman Chemical Co., Kingsport,Tenn.) is impregnated into a warp unidirectional fabric (Style A130Afrom Knytex). The fabric has a silane chemistry finish with a polyesterstitch in the weft direction. The prepregging procedure of Example 3 isfollowed, except that the fiber is heated only to 425° F. The prepreg iscured into sheets 10 in.×18 in. Eighteen plies are stacked into a heatedmold and compressed at 200 psi for ten minutes. The tool is thenquenched and the laminate panel is removed from the tool.

[0046] The panel was evaluated using a 3-point flexure test. The meanvalues for properties measured on five samples were: Displacement atMax. Load 0.1807 in. Maximum Load 875.7 lb. Stress at Max. Displacement112.9 ksi Load Modulus 5.370 Msi

EXAMPLE 5

[0047] Referring now to FIG. 3, an amorphous nylon matrix resin (Grivory21, available from EMS-American Grilion Inc., Sumpter, S.C.) was fedinto extruder 40 from hopper 42. The extruder was a Prodex one-inchextruder having a variable drive. The resin was melted in the extruderin a first zone at 485° F. and a second zone at 500° F., with theextruder turning at a rate of 40 rpm. The molten resin was forced intoan impregnation die 44 having three heating zones.

[0048] Separately, a tow of S2 glass 46 (750 yield, 933 sizing,available from Owens Corning, Corning N.Y.) is pulled from a creel 48and through a ThermCraft Tube Furnace 50 (Model 21.5-12-1ZH), the tubebeing heated to a temperature of about 850° F. Exiting the heat tube,the fiber is threaded through the impregnation die, entering through aninlet die 52 with an opening of 0.25 inch by 0.007 inch and exitingthrough a sizing die 54 with an opening of 0.25 inch by 0.009 inch.

[0049] The impregnation die face was heated to 510° F. and the resindelivery channel 56 was heated to 520° F. Die shear pins 58 in theimpregnation die were heated to 535° F. The impregnation die had asurface temperature of 625° F.

[0050] The hot fiber was pulled at a rate of about 44 ft/min. throughthe impregnation die. The resulting impregnated tow was 0.25 inch wide,0.009 inch thick, had a resin content of 46.78% by weight, and glasscontent of 53.21 and had no measurable air void content. The impregnatedtow was wound onto a frame 60 having a width of 6 inches and a length of20 inches with 175 wraps. The lay-up was then place into a mold heatedto 518° F. and compressed under 200 psi for 10 minutes, then quicklycooled to room temperature. The resulting composite panel had an averagethickness of 0.132 inches and no measurable void content. The mechanicalproperties of the panel were measured with the following results. ASTMD695-90 Compressive Properties of Rigid Plastics Method 7, width 0.5in., thickness 0.13 in. Load at Maximum (lbs.) 4562 Stress at Maximum(ksi) 70.0 % Strain at Maximum 2.497% Seg. Mod. 10-40% Maximum Load2.535 (psi * 10⁶) Displacement at Maximum (in.) 0.025 ASTM D638 TensileStrength Method 37, width 0.5 in., thickness 0.13 in. Load at Maximum(lbf) 3152 Stress at Maximum (psi * 10³) 48 % Strain at Maximum 0.893%Seg. Mod. 15-40% of Maximum Load 4.856 (psi * 10⁶) Young's Modulus15-40% (manually measured) 5.128 (psi * 10⁶) Young's Modulus 15-40%(automatic) 5.753 (psi * 10⁶) ASTM D790 Flexural Strength Method 14,width 0.974 in., thickness 0.145 in. Load at Yield (Maximum Load) (lb.)695 Stress at Yield (Maximum Load) (psi * 10³) 121 Strain at Yield(Maximum Load) (in./in.) 0.032 Displacement at Yield (Maximum Load)(in.) 0.21 Seg. Mod. 15-40% of Maximum Load 3.897 (psi * 10⁶) Young'sModulus 15-40% of Maximum Load (manually 4.192 measured) (psi * 10⁶)Young's Modulus (automatic) (psi * 10⁶) 4.015 ASTM D2344 NOL Short BeamShear Strength Method 3, span 0.675 in., width 0.26 in., depth 0.143 in.Load at Yield (Maximum Load) (lb.) 452 Laminar Shear Strength (psi *10³) 9.1

[0051] The invention has been described in detail with reference topreferred embodiments thereof. It should be understood, however, thatvariations and modifications can be made within the spirit and scope ofthe invention and of the following claims.

What is claimed is:
 1. A process for preparing a reinforced matrix resincomposition, comprising the steps of: (a) heating a fibrous reinforcingmaterial to a first temperature, (b) when heated, contacting saidreinforcing material with a resin composition at a second temperature;wherein the first temperature is greater than said second temperature.2. A process according to claim 1, wherein the reinforcing material isunder an applied shear when contacted with the resin composition.
 3. Aprocess according to claim 1, wherein the resin composition is athermoplastic composition.
 4. A process according to claim 1, whereinthe reinforcing material is a filament bundle.
 5. A process according toclaim 1, wherein the reinforcing material comprises a material selectedfrom the group consisting of glass fibers, carbon fibers, graphitefibers, polymeric fibers, aramide fibers, and mixtures thereof.
 6. Aprocess according to claim 1, wherein the reinforcing material comprisesa high silica glass fiber.
 7. A process according to claim 1, whereinthe reinforcing material is coated with a sizing or finishing material.8. A process according to claim 1, wherein the first temperature isabove the melting point, softening point, or T_(g) of the resincomposition.
 9. A process according to claim 8, wherein the firsttemperature is from about 25° F. to about 500° F. above the meltingpoint, softening point, or T_(g) of the resin composition.
 10. A processaccording to claim 8, wherein the first temperature is from about 50° F.to about 400° F. above the melting point, softening point, or T_(g) ofthe resin composition.
 11. A process according to claim 8, wherein thefirst temperature is from about 75° F. to about 350° F. above themelting point, softening point, or T_(g) of the resin composition.
 12. Aprocess according to claim 8, wherein the first temperature is fromabout 100° F. to about 300° F. above the melting point, softening point,or T_(g) of the resin composition.
 13. A process according to claim 1,wherein the first temperature is from about 350° F. to about 800° F. 14.A process according to claim 13, wherein the reinforcing materialcomprises a high silica glass fiber coated with a sizing.
 15. A processaccording to claim 14, wherein the resin composition is thermoplastic.16. A process according to claim 1, wherein the resin compositioncomprises at least one resin selected from the group consisting of ABS,acrylics, acrylonitriles, epoxies, polyarylether ketones, polyetheretherketones, amino resins, phenolics, polyamides, polyimides,polyolefins, polycarbonates, polyesters, polyetherimides, polyarylenesulfides, polyvinyl resins, polyurethanes, polysulfones, and copolymersand mixtures thereof.
 17. A process according to claim 1, wherein theresin composition comprises at least one thermosetting resin selectedfrom the group consisting of epoxies, polyesters, and phenolic resins.18. A process according to claim 1, wherein the resin composition is inthe form of a pressurized bath.
 19. A process according to claim 1,including the further step of drawing the prepreg material through ashearing mechanism.
 20. A process according to claim 1, including thefurther step of drawing the prepreg material through a sizing die.
 21. Aprocess according to claim 1, including the further step of pressing theprepreg material between rollers.
 22. A process according to claim 1,comprising a further step of forming the prepreg into a desired shape.23. A process according to claim 22, wherein the prepreg is formed by amethod selected from the group consisting of lay-up, compressionmolding, injection molding, thermoforming, blow molding, calendering,extrusion, casting, laminating, filament winding, rotational molding,transfer molding, stamping, and pultrusion operations, and combinationsthereof.
 24. A process according to claim 22, wherein the prepreg isconsolidated for a period of time of from about 1 to about 20 minutes.25. A prepreg material formed by a step of impregnating a fibrousreinforcement at a first temperature with a resin composition at asecond temperature, wherein the first temperature is greater than saidsecond temperature, and further wherein said prepreg material hassubstantially no voids.
 26. A prepreg material according to claim 25,comprising from about 25 to about 75% by weight resin.
 27. A prepregmaterial according to claim 25, comprising a thermoplastic composition.28. A prepreg material according to claim 25, comprising a thermosetcomposition.
 29. A prepreg material according to claim 25, comprising amaterial selected from the group consisting of glass fibers, carbonfibers, graphite fibers, polymeric fibers, aramide fibers, and mixturesthereof.
 30. A prepreg material according to claim 25, wherein thereinforcing material comprises a high silica glass fiber.
 31. A prepregmaterial according to claim 25, wherein the reinforcing material iscoated with a sizing or finishing material.
 32. A fiber-reinforcedarticle prepared according to the process of claim
 22. 33. Afiber-reinforced article prepared according to the process of claim 23.34. A fiber-reinforced article prepared according to the process ofclaim
 24. 35. An apparatus for preparing a reinforced matrix resincomposition, comprising a heater for heating a fibrous reinforcingmaterial to a first temperature and a container having an inlet and anoutlet for the heated fibrous reinforcing material in which the heatedreinforcing material is contacted with a resin composition; wherein thefirst temperature, as measured at said inlet, is above the meltingpoint, softening point, or T_(g) of the resin composition.
 36. Anapparatus according to claim 35, further comprising a shearing mechanismfor applying shear to the fibrous reinforcing material when the fibrousreinforcing material is in the container.
 37. An apparatus according toclaim 35, wherein said temperature is up to about 500° F. above themelting point, softening point, or T_(g) of the resin composition. 38.An apparatus according to claim 35, wherein said container furthercomprises a unit for applying pressure to the resin composition.
 39. Anapparatus according to claim 35, wherein said outlet is a sizing die.40. An apparatus according to claim 35, further including moldingequipment for forming the reinforced matrix resin composition into anarticle of a desired shape.
 41. An apparatus according to claim 35,wherein the heater is selected from the group consisting of radiantheaters, inductive heaters, infrared tunnels, ovens, and combinationsthereof.
 42. An apparatus for preparing a reinforced matrix resincomposition, comprising a heater for heating a fibrous reinforcingmaterial to a first temperature and a compressing unit for pressing theheated fibrous reinforcing material together with a resin composition;wherein the first temperature, as measured at the point where the heatedfibrous reinforcing material is first brought into contact with theresin composition, is above the melting point, softening point, or T_(g)of the resin composition.
 43. An apparatus according to claim 42,wherein the compressing unit is at least one pair of compaction rollers.44. An apparatus according to claim 42, wherein said temperature is upto about 500° F. above the melting point, softening point, or T_(g) ofthe resin composition.
 45. An apparatus according to claim 42, furthercomprising a sizing die located after said compressing unit.
 46. Anapparatus according to claim 42, further including molding equipment forforming the reinforced matrix resin composition into an article of adesired shape.
 47. An apparatus according to claim 42, wherein theheater is selected from the group consisting of radiant heaters,inductive heaters, infrared tunnels, ovens, and combinations thereof.